Imaging systems are employed in a variety of applications. For example, in surveillance applications, imaging systems can provide still or video images of a field of view, and in some cases, such systems can detect changes in the field of view, e.g., movement of a vehicle, a person, or fire and smoke.
When covering a relatively large area, for example in the order of an acre in size, it may be advantageous to obtain wide field imagery concurrent with detailed zooms of specific areas of interest, for example based on motion to identify people and vehicles.
To achieve above, some surveillance systems use multiple cameras in a single enclosure with a two-part design, the first part consisting of an array of fixed cameras, referred to as sockets in some cases, for viewing the wide field, and a second part consisting of panable tiltable zoom (PTZ) camera to acquire detailed close-up imagery as directed by the first part, either automatically or as specified by an operator.
The primary purpose of most surveillance systems in use today is identification of people and vehicles. The two-part system described above can effectively provide video coverage of a large area, for example a parking lot or the interior of a warehouse or a campus environment, with sufficient image quality and detail for identification purposes.
U.S. Pat. No. 6,215,519 discloses such a surveillance system having a first and second image collection devices, with the second being guided by the first device and mounted within a common framework. At least one known commercial video surveillance system, which is disclosed in European Patent Specification EP 1,579,399 B1, includes a compound camera assembly including eight video cameras mounted in a single housing and including a PTZ camera to cover a hemispherical or semi-hemispherical field of view.
Camera designs disclosed in the above references utilize a combination of sockets (for the reference cameras) covering the wide field and a single PTZ type camera to provide zoom guided by software control. The camera assembly is typically held within a common enclosure to provide a fixed geometric calibration framework and also protect the system from the environment.
The construction of camera designs with multiple sockets is complex and costly and presents multiple failure modes when such systems are installed outdoors and exposed to the elements. Thus, there is a need for improved cameras and associated surveillance systems.